HABITS IN MAMMAL. 



8. Sternum well developed.— The anterior part of the trunk 

 requires rigidity, great strength and ample surfaces for the 



for muscular attachment prominent (e. - armadillos) P In the 

 moles change of position of the fore limb is correlated not only 

 with the broadening but especially with the elongation of the 

 presternum ; at the same time the clavicle is extremely broad, 

 and shortened so that the limbs may project as little as possible 

 from the sides of the body ; the limbs arc but slightly shortened, 

 so that the leverage of the muscles is unaffected. In I'hryso 

 chloris this need is met by the invagination, as it were, of the 

 walls of the thorax for the reception of the arms, the ribs and 

 sternum being convex inward. The clavicle is usually, as in 

 Chrysochloris, curved backward from the sternum, so that the 

 shoulder may slope gradually forward and not be an angular 

 projection interfering with progress through the earth. 



fore limbs being the principal organs for digging are well devel- 

 oped, while the tuberosities, ridges, etc., for the insertion of mus- 

 cles are very prominent. Sesamoid bones are frequently devel- 

 oped in the palms, as in Echidna where also the breadth of the 



The humerus is usually stout and broad as in Talpa, Phas- 



ridges'. These are carried to an extreme in Talpa where the 

 deltoid ridge joins the inner tuberosity above. The olecranon 

 process is alwavs stronglv developed. A supracondylar foramen 



1 0. Ilium and ischium rod-like, parallel to the vertebral column 



pushing the body through the earth, their point of attachment 

 to the body must be firm and they must deliver the forward 

 thrust in a more or less horizontal plane. So we find that the 

 1 s long It >d usually throughout its entire length to 

 the vertebral column ; this is especially true of the moles. 



1 1 . Bones of hind limb not so strongly de veloped as those of 

 fore limb. Besides pushing the bodv forward the hind limbs 



